MySql主从

mysql主从

1. 主从的简介

主从就是主从复制，简单来说，是使用两个或两个以上相同的数据库，将一个数据库当做主数据库，而另一个数据库当做从数据库。在主数据库中进行相应操作时，从数据库记录下所有主数据库的操作，使其二者一模一样。

1.1 主从作用

• 实时灾备，用于故障切换
• 读写分离，提供查询服务
• 备份，避免影响业务

1.2 主从形式

2. 主从复制原理

主从复制步骤：

• 主库将所有的写操作记录到binlog日志中并生成一个log dump线程，将binlog日志传给从库的I/O线程
• 从库生成两个线程，一个I/O线程，一个SQL线程
  • I/O线程去请求主库的binlog，并将得到的binlog日志写到relay log（中继日志） 文件中
  • SQL线程，会读取relay log文件中的日志，并解析成具体操作，来实现主从的操作一致，达到最终数据一致的目的

3. 主从复制配置

主从复制配置步骤：

1. 确保从数据库与主数据库里的数据一样
2. 在主数据库里创建一个同步账号授权给从数据库使用
3. 配置主数据库（修改配置文件）
4. 配置从数据库（修改配置文件）

需求：
搭建两台MySQL服务器，一台作为主服务器，一台作为从服务器，主服务器进行写操作，从服务器进行读操作

3.1 mysql安装

分别在主从两台服务器上安装mysql-5.7版本，此处略过安装步骤，若有疑问请参考《mysql基础》与《mysql进阶》两篇文章。

3.2 mysql主从配置

情景一：公司有两台数据库都没有数据，我们来配置主从复制

环境说明：

数据库角色	IP	应用与系统版本	有无数据
主数据库master	192.168.153.132	mariadb/redhat8	无数据
从数据库slave	192.168.153.133	mariadb/redhat8	无数据

准备工作（安装mysql关闭防火墙）

//master主机
[root@master ~]# yum -y install mariadb*
[root@master ~]# systemctl start mariadb
[root@master ~]# ss -antl
State     Recv-Q     Send-Q         Local Address:Port         Peer Address:Port    
LISTEN    0          80                   0.0.0.0:3306              0.0.0.0:*       
LISTEN    0          128                  0.0.0.0:22                0.0.0.0:*       
LISTEN    0          128                     [::]:22                   [::]:* 
[root@master ~]# systemctl stop firewalld
[root@master ~]# systemctl disable firewalld
[root@master ~]# setenforce 0
//slave主机
[root@slave ~]# yum -y install mariadb*
[root@slave ~]# systemctl start mariadb
[root@slave ~]# ss -antl
State     Recv-Q     Send-Q         Local Address:Port         Peer Address:Port    
LISTEN    0          80                   0.0.0.0:3306              0.0.0.0:*       
LISTEN    0          128                  0.0.0.0:22                0.0.0.0:*       
LISTEN    0          128                     [::]:22                   [::]:* 
[root@slave ~]# systemctl stop firewalld
[root@slave ~]# systemctl disable firewalld
[root@slave ~]# setenforce 0

在主数据库里创建一个同步账号授权给从数据库使用

//master主机
[root@master ~]# mysql
Welcome to the MariaDB monitor.  Commands end with ; or g.
Your MariaDB connection id is 8
Server version: 10.3.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

MariaDB [(none)]> grant replication slave on *.* to 'lc'@'192.168.153.133' identified by '123456';  
Query OK, 0 rows affected (0.000 sec)

MariaDB [(none)]> flush privileges;
Query OK, 0 rows affected (0.001 sec)

MariaDB [(none)]> quit
Bye

//slave主机
[root@slave ~]# mysql -ulc -p123456 -h192.168.153.132   //测试连接
Welcome to the MariaDB monitor.  Commands end with ; or g.
Your MariaDB connection id is 9
Server version: 10.3.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

MariaDB [(none)]> quit
Bye

配置主数据库

[root@master ~]# vim /etc/my.cnf

#
# This group is read both both by the client and the server
# use it for options that affect everything
#
//添加下面三行配置，=号左边格式要一样，右边格式也要一样
[mysqld]
log-bin = mysql_bin  //启用binlog日志
server-id = 10	   //数据库服务器唯一标识符（从库的server-id值必须大于主库的值）
 
[root@master ~]# systemctl restart mariadb  //重启mariadb

//查看主库状态
[root@master ~]# mysql
MariaDB [(none)]> show master status;    
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql_bin.000001 |      328 |              |                  |
+------------------+----------+--------------+------------------+
1 row in set (0.000 sec)

MariaDB [(none)]> 

配置从数据库

[root@slave ~]# vim /etc/my.cnf

#
# This group is read both both by the client and the server
# use it for options that affect everything
#
[client-server]

[mysqld]
relay-log = myrelay    //启用中继日志relay-log
server-id = 20         //数据库服务器唯一标识符（从库的server-id值必须大于主库的值）

[root@slave ~]# systemctl restart mariadb   //重启mariadb

//配置并启动主从复制
[root@slave ~]# mysql
MariaDB [(none)]>  change master to master_host='192.168.153.132',master_user='lc',master_password='123456',master_log_file='mysql_bin.000001',master_log_pos=328;
Query OK, 0 rows affected (0.010 sec)

MariaDB [(none)]> start slave;      
Query OK, 0 rows affected (0.002 sec)

MariaDB [(none)]> show slave statusG;     //查看从数据库的状态
*************************** 1. row ***************************
                Slave_IO_State: Waiting for master to send event
                   Master_Host: 192.168.153.132
                   Master_User: lc
                   Master_Port: 3306
                 Connect_Retry: 60
               Master_Log_File: mysql_bin.000001
           Read_Master_Log_Pos: 328
                Relay_Log_File: myrelay.000002
                 Relay_Log_Pos: 555
         Relay_Master_Log_File: mysql_bin.000001
              Slave_IO_Running: Yes     //这里一定要是yes
             Slave_SQL_Running: Yes		//这里一定要是yes
					
Slave_Non_Transactional_Groups: 0
    Slave_Transactional_Groups: 0
1 row in set (0.000 sec)

测试验证

在主服务器的school库的student表中插入数据：

[root@master ~]# mysql
Welcome to the MariaDB monitor.  Commands end with ; or g.
Your MariaDB connection id is 11
Server version: 10.3.17-MariaDB-log MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

MariaDB [(none)]> create database school;
Query OK, 1 row affected (0.000 sec)

MariaDB [(none)]> use school;
Database changed
MariaDB [school]> create table student(id int not null primary key auto_increment,name varchar(20),age tinyint);
Query OK, 0 rows affected (0.017 sec)

MariaDB [school]> insert student(name,age)values('tom',15),('eric',21),('jerry',19);Query OK, 3 rows affected (0.002 sec)
Records: 3  Duplicates: 0  Warnings: 0

MariaDB [school]> select * from student;
+----+-------+------+
| id | name  | age  |
+----+-------+------+
|  1 | tom   |   15 |
|  2 | eric  |   21 |
|  3 | jerry |   19 |
+----+-------+------+
3 rows in set (0.000 sec)

MariaDB [school]> quit
Bye
[root@master ~]#

在从数据库中查看数据是否同步：

[root@slave ~]# mysql
Welcome to the MariaDB monitor.  Commands end with ; or g.
Your MariaDB connection id is 12
Server version: 10.3.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| school             |
+--------------------+
4 rows in set (0.000 sec)

MariaDB [(none)]> use school;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
MariaDB [school]> show tables;
+------------------+
| Tables_in_school |
+------------------+
| student          |
+------------------+
1 row in set (0.000 sec)

MariaDB [school]> select * from student;

+----+-------+------+
| id | name  | age  |
+----+-------+------+
|  1 | tom   |   15 |
|  2 | eric  |   21 |
|  3 | jerry |   19 |
+----+-------+------+
3 rows in set (0.000 sec)

MariaDB [school]>

验证完毕数据同步

情景一：公司有两台数据库，主数据库中有数据，我们来配置主从复制

环境说明

数据库角色	IP	应用与系统版本	有无数据
主数据库master	192.168.153.132	mariadb/redhat8	有数据
从数据库slave	192.168.153.133	mariadb/redhat8	无数据

准备工作（安装mysql关闭防火墙）

//master主机
[root@master ~]# yum -y install mariadb*
[root@master ~]# systemctl start mariadb
[root@master ~]# ss -antl
State     Recv-Q     Send-Q         Local Address:Port         Peer Address:Port    
LISTEN    0          80                   0.0.0.0:3306              0.0.0.0:*       
LISTEN    0          128                  0.0.0.0:22                0.0.0.0:*       
LISTEN    0          128                     [::]:22                   [::]:* 
[root@master ~]# systemctl stop firewalld
[root@master ~]# systemctl disable firewalld
[root@master ~]# setenforce 0
//slave主机
[root@slave ~]# yum -y install mariadb*
[root@slave ~]# systemctl start mariadb
[root@slave ~]# ss -antl
State     Recv-Q     Send-Q         Local Address:Port         Peer Address:Port    
LISTEN    0          80                   0.0.0.0:3306              0.0.0.0:*       
LISTEN    0          128                  0.0.0.0:22                0.0.0.0:*       
LISTEN    0          128                     [::]:22                   [::]:* 
[root@slave ~]# systemctl stop firewalld
[root@slave ~]# systemctl disable firewalld
[root@slave ~]# setenforce 0

模拟主数据库master有数据

[root@master ~]# mysql
Welcome to the MariaDB monitor.  Commands end with ; or g.
Your MariaDB connection id is 8
Server version: 10.3.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

MariaDB [(none)]> create database info;
Query OK, 1 row affected (0.000 sec)

MariaDB [(none)]> use info
Database changed
MariaDB [info]> create table basic(id int not null primary key auto_increment,name varchar(50),job varchar(50));
Query OK, 0 rows affected (0.013 sec)

MariaDB [info]> insert basic (name,job) values ('tom','engineer'),('jerry','office');
Query OK, 2 rows affected (0.001 sec)
Records: 2  Duplicates: 0  Warnings: 0

MariaDB [info]> create table salary(name varchar(50),salary float);
Query OK, 0 rows affected (0.005 sec)

MariaDB [info]> insert salary values('tom',8000),('jerry',8500),('zhangshan',9000),('lisi',7500);
Query OK, 4 rows affected (0.001 sec)
Records: 4  Duplicates: 0  Warnings: 0

MariaDB [info]> show databases;
+--------------------+
| Database           |
+--------------------+
| info               |
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
4 rows in set (0.001 sec)

MariaDB [info]> use info;
Database changed
MariaDB [info]> show tables;
+----------------+
| Tables_in_info |
+----------------+
| basic          |
| salary         |
+----------------+
2 rows in set (0.000 sec)

MariaDB [info]> select * from basic;
+----+-------+----------+
| id | name  | job      |
+----+-------+----------+
|  1 | tom   | engineer |
|  2 | jerry | office   |
+----+-------+----------+
2 rows in set (0.000 sec)

MariaDB [info]> select * from salary;
+-----------+--------+
| name      | salary |
+-----------+--------+
| tom       |   8000 |
| jerry     |   8500 |
| zhangshan |   9000 |
| lisi      |   7500 |
+-----------+--------+
4 rows in set (0.000 sec)

MariaDB [info]> 

确保从数据库与主数据库里的数据一样

为确保从数据库与主数据库里的数据一样，先全备主数据库并还原到从数据库中

//查看主数据口有哪些库
[root@master ~]# mysql -uroot -e 'show databases;'
+--------------------+
| Database           |
+--------------------+
| info               |
| information_schema |
| mysql              |
| performance_schema |
+--------------------+

//查看从数据口有哪些库
[root@slave ~]# mysql -uroot -e 'show databases;'
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+

//全备主库
//全备主库时需要另开一个终端，给数据库加上读锁，避免在备份期间有其他人在写入导致数据不一致
MariaDB [(none)]> flush tables with read lock;
Query OK, 0 rows affected (0.001 sec)
//此锁表的终端必须在备份完成以后才能退出
//quit退出后，自动取消读锁

//此时已经无法写入数据了
MariaDB [(none)]> use info;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
MariaDB [info]> select * from basic
    -> ;
+----+-------+----------+
| id | name  | job      |
+----+-------+----------+
|  1 | tom   | engineer |
|  2 | jerry | office   |
+----+-------+----------+
2 rows in set (0.000 sec)
//插入数据失败
MariaDB [info]> insert basic(name,job)values('zhangshan','cleaner');
ERROR 1223 (HY000): Can't execute the query because you have a conflicting read lock

//再开启一个master主机终端
[root@master ~]# mysqldump -uroot --all-databases > all.sql  //做一个全量备份
[root@master ~]# ls
all.sql  anaconda-ks.cfg
[root@master ~]# scp all.sql 192.168.153.133:/root/    //把全备文件拷贝到slave主机的root目录下
The authenticity of host '192.168.153.133 (192.168.153.133)' can't be established.
ECDSA key fingerprint is SHA256:yFpgARX7WkH6WN29fHahmzlDbrUxFzaNBw5Pg8neBd4.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '192.168.153.133' (ECDSA) to the list of known hosts.
root@192.168.153.133's password:           
all.sql  100%  469KB  36.1MB/s   00:00  

//备份完之后，quit退出，读锁自动解除
MariaDB [info]> quit
Bye


//slave主机
//在从库上恢复主库的备份并查看从库有哪些库，确保与主库一致
[root@slave ~]# ls   //可以看到all。sql文件已经拷贝进来了
all.sql  anaconda-ks.cfg
[root@slave ~]# mysql -e 'show databases;'   //此时还没有恢复全备
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
[root@slave ~]# mysql < all.sql    //恢复全备
[root@slave ~]# mysql -e 'show databases;'    //可以看到和master主数据库内容一样了
+--------------------+
| Database           |
+--------------------+
| info               |
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
[root@slave ~]#

在主数据库里创建一个同步账号授权给从数据库使用

//master主机
[root@master ~]# mysql
MariaDB [(none)]> grant replication slave on *.* to 'lc'@'192.168.153.133' identified by '123456';
Query OK, 0 rows affected (0.001 sec)

MariaDB [(none)]> flush privileges;
Query OK, 0 rows affected (0.001 sec)


//slave主机
[root@slave ~]#  mysql -ulc -p123456 -h192.168.153.132     //测试连接
Welcome to the MariaDB monitor.  Commands end with ; or g.
Your MariaDB connection id is 14
Server version: 10.3.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

MariaDB [(none)]> quit
Bye

配置主数据库

[root@master ~]# vim /etc/my.cnf

#
# This group is read both both by the client and the server
# use it for options that affect everything
#
//添加下面三行配置，=号左边格式要一样，右边格式也要一样
[mysqld]
log-bin = mysql_bin  //启用binlog日志
server-id = 10	   //数据库服务器唯一标识符（从库的server-id值必须大于主库的值）
 
[root@master ~]# systemctl restart mariadb  //重启mariadb

//查看主库状态
[root@master ~]# mysql
MariaDB [(none)]> show master status;    
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql_bin.000001 |      328 |              |                  |
+------------------+----------+--------------+------------------+
1 row in set (0.000 sec)

MariaDB [(none)]> 

配置从数据库

[root@slave ~]# vim /etc/my.cnf

#
# This group is read both both by the client and the server
# use it for options that affect everything
#
[client-server]

[mysqld]
relay-log = myrelay    //启用中继日志relay-log
server-id = 20         //数据库服务器唯一标识符（从库的server-id值必须大于主库的值）

[root@slave ~]# systemctl restart mariadb   //重启mariadb

//配置并启动主从复制
[root@slave ~]# mysql
MariaDB [(none)]> change master to
master_host='192.168.153.132',master_user='lc',master_password='123456',master_log_file='mysql_bin.000001',master_log_pos=328;

MariaDB [(none)]> start slave;
Query OK, 0 rows affected (0.001 sec)

MariaDB [(none)]> show slave statusG   //查看从数据库的状态
*************************** 1. row ***************************
                Slave_IO_State: Waiting for master to send event
                   Master_Host: 192.168.153.132
                   Master_User: lc
                   Master_Port: 3306
                 Connect_Retry: 60
               Master_Log_File: mysql_bin.000001
           Read_Master_Log_Pos: 328
                Relay_Log_File: myrelay.000002
                 Relay_Log_Pos: 555
         Relay_Master_Log_File: mysql_bin.000001
              Slave_IO_Running: Yes   //这里一定要是yes
             Slave_SQL_Running: Yes	  //这里一定要是yes

测试验证

在从服务器上查看一下info库里basic的数据

[root@slave ~]# mysql
Welcome to the MariaDB monitor.  Commands end with ; or g.
Your MariaDB connection id is 11
Server version: 10.3.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| info               |
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
4 rows in set (0.001 sec)

MariaDB [(none)]> use info;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
MariaDB [info]> show tables;
+----------------+
| Tables_in_info |
+----------------+
| basic          |
| salary         |
+----------------+
2 rows in set (0.000 sec)

MariaDB [info]> select * from basic;
+----+-------+----------+
| id | name  | job      |
+----+-------+----------+
|  1 | tom   | engineer |
|  2 | jerry | office   |
+----+-------+----------+
2 rows in set (0.000 sec)

MariaDB [info]>

在主数据库中的info库中的basic表里插入一条数据

[root@master ~]# mysql
Welcome to the MariaDB monitor.  Commands end with ; or g.
Your MariaDB connection id is 11
Server version: 10.3.17-MariaDB-log MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| info               |
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
4 rows in set (0.001 sec)

MariaDB [(none)]> use info;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
MariaDB [info]> show tables;
+----------------+
| Tables_in_info |
+----------------+
| basic          |
| salary         |
+----------------+
2 rows in set (0.000 sec)

MariaDB [info]> insert basic(name,job)values('lc','student')  //插入一个数据
    -> ;
Query OK, 1 row affected (0.002 sec)

MariaDB [info]> 

在从数据库上查看一下basic表的信息是否同步

[root@slave ~]# mysql
Welcome to the MariaDB monitor.  Commands end with ; or g.
Your MariaDB connection id is 12
Server version: 10.3.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| info               |
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
4 rows in set (0.000 sec)

MariaDB [(none)]> use info;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
MariaDB [info]> show tables;
+----------------+
| Tables_in_info |
+----------------+
| basic          |
| salary         |
+----------------+
2 rows in set (0.000 sec)

MariaDB [info]> select * from basic;
+----+-------+----------+
| id | name  | job      |
+----+-------+----------+
|  1 | tom   | engineer |
|  2 | jerry | office   |
|  3 | lc    | student  |
+----+-------+----------+
3 rows in set (0.000 sec)

MariaDB [info]>

验证完毕数据同步